Tube-bending machine



1 NOV. 26, 194Q. C "E HATHQRN 2,223,015

TUBE-BENDING MACHINE Filed May 27, 1937 v 2 Sheets-Sheet 2 FIGFZ.

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INVENTOR CHARLES E. HATHORH;

ATTORNEY I 1sFIq.4.-. 7

Patented Nov. 26, 194% UNITED STATES 2,223,015 TUBE-BENDING MACHINECharles E. Hathorn, Kenmore, N. Y., assignor to Curtiss-WrightCorporation, a corporation of Delaware Application May 27, 1937, SerialNo. 144,995

12 Claims. (Cl. 153-49) This invention relates to tube-bending machines,and is particularly concerned with such improvements as will permit ofthe bending of large diameter thin-walled tubes without buckling of thetube material.

In the aircraft art, particularly, considerable use is made ofrelatively large diameter thinwalled tubing of stainless steel,aluminum, or other metals, in connection with exhaust systems,

oil lines, and other parts of the power plant, and it is frequentlynecessary to provide tubes which are bent on a relatively sharp curve.Little difiiculty is experienced when tubes are to be bent. on a largeradius, but when sharp bends are attempted with conventional equipment,the tensile strain on the outer side of the tube, and the compressivestrain on the inner side of the tubing, tends to deform the material insuch a way as to make the bend unsatisfactory. Particularly, thematerial at the inside of the bend tends to buckle into waves orripples, resulting in an unsightly article and one which ofiers greaterresistance to fluid flow therethrough than is desirable.

An object of the present invention is to provide means by which sharpbends may be made in tubes to the elimination of corrugations in theresultant bent tube. A further object of the invention is to providemeans which may be installed on existing types of tube bending machinesto adapt them for short radius bends on thinwalled tubing.

Further objects will become apparent from a reading of the sub-joinedspecification and claims, together with an examination of theaccompanying drawings, in which similar numbers indicate similar parts,and in which:

Fig. 1 is a perspective view of the table of a tube bending machineincorporating the invention;

Fig. 2 is a plan of the work station of a tube bending machine, partlyin section, to show the details of the invention;

Fig. 3 is a side elevation of the work table of the machine; and

Fig. 4 is a section on the line 4-4 of Fig. 2. The general elements ofthe machine pictured are conventional, and include a power rotated worktable ID, upon which is mounted a clamp assembly H, within which one endl2 of a tube I3 is tightly held. A central bending arbor, designated inits entirety as I4, is mounted upon the table l0 and the clampingassembly ll holds the tube tangent to the arbor It. A base 15 of themachine carries a reciprocable slide l6, movable toward and away fromthe arbor it by a hydraulic cylinder assembly H, the slide I6 carrying asupport [8 provided with rollers 89 over which a guide 20 istranslatable, said guide having a forming die 2! attached thereto formovement with the tube 53 as same is drawn around the arbor it. As shownin Fig. 2, a mandrel 22, provided with an end concentric with the arborI4, is inserted within the tube to prevent the collapse thereof. The die2! is formed to embrace substantially half of the circumference of thetube l2, as shown in Fig. 4, and the arbor I4 is likewise formed toembrace substantially half of the tube. Accordingly, when the straighttube is assembled in the machine, and when the table In is rotated, theclamp ll draws the tube around the arbor l4, bending same to the desiredextent.

When the arbor is of small diameter, and when it is of solidconstruction according to conventional practice, corrugations appear inthe finished bent tube which are most objectionable.

To overcome this, I provide an arbor H such as that shown in theillustrations, which comprises a plurality of parts, including sideplates 23 and 24 bolted to and movable with the table ill, the sideplates embracing a sheave- 25 mounted for rotation with respect to theplates 23 and 24. Said sheave, around its periphery, may be formed withherringbone serrations 26, and the inside of the sheave is formed as aninternal gear 21. A plurality of planet pinions 28 are journaled in theside plates 23 and 24, and engage the gear 21, a sun gear being mountedconcentric with the arbor I4, the sun gear being keyed to the shaft ofan electric motor or other suitable power source 29, carried by theplate 23. By the planet gear system indicated, the sheave 25 is rotatedrelative to the side plates 23 and 24, when the motor 29 is energized.

During the tube bending operation, the side 'plates 23 and 24 rotatewith the table l0, but

the sheave 25 rotates at a greater rate of speed so that, during thebending operation, the sheave 25 irons out any incipient corrugationswhich are likely to form, the action thus obtained being somewhatsimilar to a spinning operation where the excess metal accumulating onthe inner wall of the bend is distributed outwardly around the tubeperiphery by virtue of the ironing action. In use, the sheave 25 and thetube will be well lubricated so that the ironing operation aboveindicated will avoid tearing the surface of the tube 52.

It has been found that the corrugations flowin from the ordinary type ofbending machine are of more or less herringbone form, that portion ofthe corrugation which is in the plane of symmetry of the tube laggingbehind the lateral portions of the corrugation. Accordingly, then, theherringbone elements 26 of the sheave 25 may be formed in opposite senseto have a greater ironing effect upon the incipient corrugations. Or,alternately, the corrugations of the sheave 25 may be formed straightacross the face of the sheave.

It has been found that the corrugations in tially eliminated. Themandrel 22 acts as an abutment against which the sheave operates, andduring the bending operation, substantial pressure is maintained uponthe guide 2!, which moves with the tube, by the hydraulic mechanism ll.

While I have described my invention in detail in its present preferredembodiment, it will be obvious to those skilled in the art, afterunderstanding my invention, that various changes and modifications maybe made therein without departing from the spirit or scope thereof. Iaim in the appended claims to cover all such modifications and changes.

I claim as my invention:

1. In a tube-bending machine comprising a rotatable work table; a clampthereon. for engagement with a tube to be bent; a stationary guiding diefor the tube; an arbor for forming a bend in the tube comprising sideplatesrotatable with the table and a sheave embraced by said plates andengageable with a portion of the tube to be bent; and means for rotatingsaid sheave relative to said plates and table.

2. In a tube-bending machine, an arbor comprising a plurality ofrelatively rotatable elements engageable with a tube to be bent, andmeans for rotating said elements with respect to each other.

3. In a bending machine, a work table, means to clamp work to be bent tothe table, a bending arbor engageable with the work, means to rotatesaid arbor relative to the table, a bending arm holding the work inengagement with the arbor, and means to rotate said arm and tablerelative to each other at a speed diiierent from the rotational speed ofthe arbor relative to the table.

4. In a bending machine, a clamping member for work to be bent, anarbor, means for relatively rotating said arbor and clamping member, abending arm engaging the work to be bent and adapted to bend the workabout the arbor, and means for relatively rotating the bending arm andclamping member about the arbor center but at a speed different fromthat of the arbor relative to the clamping member.

5. In a bending machine comprising a clamp and reaction memberrelatively rotatable about a center, means to effect said rotation, anarbor on said center around which work held by said clamp and bearing onsaid reaction member is adapted to beb'ent, and power means for rotatingsaid arbor at a speed greater than that of said clamp relative to saidreaction member.

6. In a bending machine, a work table, means to clamp work to be bent tothe table, a bending arbor engageable with the work, means to rotatesaid arbor relative to the table, a bending arm holding the work inengagement with the arbor, and means to rotate said arm and tablerelative to each other at a speed different from-the rotational speed ofthe arbor relative to the table, said means comprising a motor drivenepicyclic gear train contained within the arbor for driving said arborrelative to the clamp.

'7. In a tube-bending machine, a work table,

means forrotating the table, a bending arbor for forming a tube to bebent, power means for rotating said arbor with respect to said table andtube during table rotation, said arbor having corrugations across thesurface thereof for engagement with the tube for ironing incipientcorrugations which might tend to form upon the tube, and reactionmembers bearing on the surface thereof for engagement with theytube forironing incipient corrugations which might tend to form upon the tube,and reaction members bearing on the tube on opposite sides of the arbor,one of which members is fixed and the other of which is secured to thetable.

9. In a tube-bending machine; a bending arbor comprising an annularmember externally circumferentially grooved and provided with gearteeth, side plates carrying said arbor, planet pinions journaled in saidside plates engaging said gear teeth, and a sun pinion journaled in theplates drivably engaging said planet pinions; 8. power rotated worktable upon which the side plates are rigidly mounted, means for drivingsaid sun pinion whereby the annular member is forced to rotate withrespect to a table,

that of the table, and a rotationally fixed member bearing on the tubeon the other side of the arbor from that part of the tube secured to thetable.

11. In a tube-bending machine, a work table on which a tube to be bentis secured, means for rotating said table, a bending arbor bearing onthe tube for forming same and mounted for rotation with respect to saidtable, said arbor having corrugations across the surface thereof forengagement with the tube and for ironing incipient corrugations whichtend to form upon the tube, means for rotating said arbor in the samedirection as the work table and at a greater speed than the speed of thework table, and a substantially flxed reaction member bearing on thetube on the other side thereof from the.

